LinuxLists.cc - [PATCH v3 2/3] powerpc/powernv: wire up rng during setup

2022-06-11 16:09:22

Subject: [PATCH v3 2/3] powerpc/powernv: wire up rng during setup_arch

2022-06-11 16:51:48

Subject: Re: [PATCH v3 2/3] powerpc/powernv: wire up rng during setup_arch

Le 11/06/2022 à 17:10, Jason A. Donenfeld a écrit :
> The platform's RNG must be available before random_init() in order to be
> useful for initial seeding, which in turn means that it needs to be
> called from setup_arch(), rather than from an init call. Fortunately,
> each platform already has a setup_arch function pointer, which means
> it's easy to wire this up. This commit also removes some noisy log
> messages that don't add much.
>
> Cc: [email protected]
> Cc: Michael Ellerman <[email protected]>
> Cc: Christophe Leroy <[email protected]>
> Fixes: a4da0d50b2a0 ("powerpc: Implement arch_get_random_long/int() for powernv")
> Signed-off-by: Jason A. Donenfeld <[email protected]>

Reviewed-by: Christophe Leroy <[email protected]>

> ---
> arch/powerpc/platforms/powernv/powernv.h | 2 ++
> arch/powerpc/platforms/powernv/rng.c | 18 +++++-------------
> arch/powerpc/platforms/powernv/setup.c | 2 ++
> 3 files changed, 9 insertions(+), 13 deletions(-)
>
> diff --git a/arch/powerpc/platforms/powernv/powernv.h b/arch/powerpc/platforms/powernv/powernv.h
> index e297bf4abfcb..fd3f5e1eb10b 100644
> --- a/arch/powerpc/platforms/powernv/powernv.h
> +++ b/arch/powerpc/platforms/powernv/powernv.h
> @@ -42,4 +42,6 @@ ssize_t memcons_copy(struct memcons *mc, char *to, loff_t pos, size_t count);
> u32 __init memcons_get_size(struct memcons *mc);
> struct memcons *__init memcons_init(struct device_node *node, const char *mc_prop_name);
>
> +void powernv_rng_init(void);
> +
> #endif /* _POWERNV_H */
> diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c
> index e3d44b36ae98..c86bf097e407 100644
> --- a/arch/powerpc/platforms/powernv/rng.c
> +++ b/arch/powerpc/platforms/powernv/rng.c
> @@ -17,6 +17,7 @@
> #include <asm/prom.h>
> #include <asm/machdep.h>
> #include <asm/smp.h>
> +#include "powernv.h"
>
> #define DARN_ERR 0xFFFFFFFFFFFFFFFFul
>
> @@ -84,24 +85,20 @@ static int powernv_get_random_darn(unsigned long *v)
> return 1;
> }
>
> -static int __init initialise_darn(void)
> +static void __init initialise_darn(void)
> {
> unsigned long val;
> int i;
>
> if (!cpu_has_feature(CPU_FTR_ARCH_300))
> - return -ENODEV;
> + return;
>
> for (i = 0; i < 10; i++) {
> if (powernv_get_random_darn(&val)) {
> ppc_md.get_random_seed = powernv_get_random_darn;
> - return 0;
> + return;
> }
> }
> -
> - pr_warn("Unable to use DARN for get_random_seed()\n");
> -
> - return -EIO;
> }
>
> int powernv_get_random_long(unsigned long *v)
> @@ -163,14 +160,12 @@ static __init int rng_create(struct device_node *dn)
>
> rng_init_per_cpu(rng, dn);
>
> - pr_info_once("Registering arch random hook.\n");
> -
> ppc_md.get_random_seed = powernv_get_random_long;
>
> return 0;
> }
>
> -static __init int rng_init(void)
> +void __init powernv_rng_init(void)
> {
> struct device_node *dn;
> int rc;
> @@ -188,7 +183,4 @@ static __init int rng_init(void)
> }
>
> initialise_darn();
> -
> - return 0;
> }
> -machine_subsys_initcall(powernv, rng_init);
> diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
> index 824c3ad7a0fa..a5fcb6796b22 100644
> --- a/arch/powerpc/platforms/powernv/setup.c
> +++ b/arch/powerpc/platforms/powernv/setup.c
> @@ -203,6 +203,8 @@ static void __init pnv_setup_arch(void)
> pnv_check_guarded_cores();
>
> /* XXX PMCS */
> +
> + powernv_rng_init();
> }
>
> static void __init pnv_init(void)

2022-06-19 11:54:26

by Michael Ellerman

[permalink] [raw]

Subject: Re: [PATCH v3 2/3] powerpc/powernv: wire up rng during setup_arch

"Jason A. Donenfeld" <[email protected]> writes:
> The platform's RNG must be available before random_init() in order to be
> useful for initial seeding, which in turn means that it needs to be
> called from setup_arch(), rather than from an init call. Fortunately,
> each platform already has a setup_arch function pointer, which means
> it's easy to wire this up. This commit also removes some noisy log
> messages that don't add much.
>
> Cc: [email protected]
> Cc: Michael Ellerman <[email protected]>
> Cc: Christophe Leroy <[email protected]>
> Fixes: a4da0d50b2a0 ("powerpc: Implement arch_get_random_long/int() for powernv")
> Signed-off-by: Jason A. Donenfeld <[email protected]>
> ---
> arch/powerpc/platforms/powernv/powernv.h | 2 ++
> arch/powerpc/platforms/powernv/rng.c | 18 +++++-------------
> arch/powerpc/platforms/powernv/setup.c | 2 ++
> 3 files changed, 9 insertions(+), 13 deletions(-)
>
...
> diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
> index 824c3ad7a0fa..a5fcb6796b22 100644
> --- a/arch/powerpc/platforms/powernv/setup.c
> +++ b/arch/powerpc/platforms/powernv/setup.c
> @@ -203,6 +203,8 @@ static void __init pnv_setup_arch(void)
> pnv_check_guarded_cores();
>
> /* XXX PMCS */
> +
> + powernv_rng_init();
> }

This crashes on power8 because it's too early to call kzalloc() in
rng_create(), and it's also too early to setup the percpu variables in
there.

I'll rework it and post a v4.

cheers

2022-06-19 20:33:22

by Jason A. Donenfeld

[permalink] [raw]

Subject: Re: [PATCH v3 2/3] powerpc/powernv: wire up rng during setup_arch

Hi Michael,

On Sun, Jun 19, 2022 at 1:49 PM Michael Ellerman <[email protected]> wrote:
> This crashes on power8 because it's too early to call kzalloc() in
> rng_create(), and it's also too early to setup the percpu variables in
> there.
>
> I'll rework it and post a v4.

Oh, darn. Sorry about that. Thanks for reworking it.

Jason

2022-06-20 14:59:07

by Jason A. Donenfeld

[permalink] [raw]

Subject: [PATCH v4] powerpc/powernv: wire up rng during setup_arch

The platform's RNG must be available before random_init() in order to be
useful for initial seeding, which in turn means that it needs to be
called from setup_arch(), rather than from an init call. Fortunately,
each platform already has a setup_arch function pointer, which means we
can wire it up that way. Complicating things, however, is that POWER8
systems need some per-cpu state and kmalloc, which isn't available at
this stage. So we split things into an early phase and a late phase,
with the early phase working well enough to seed the RNG with a
spinlock, before later getting fast per-cpu allocations. This commit
also removes some noisy log messages that don't add much.

Cc: [email protected]
Cc: Michael Ellerman <[email protected]>
Reviewed-by: Christophe Leroy <[email protected]>
Fixes: a4da0d50b2a0 ("powerpc: Implement arch_get_random_long/int() for powernv")
Signed-off-by: Jason A. Donenfeld <[email protected]>
---
arch/powerpc/platforms/powernv/powernv.h | 2 +
arch/powerpc/platforms/powernv/rng.c | 68 ++++++++++++++++++------
arch/powerpc/platforms/powernv/setup.c | 2 +
3 files changed, 55 insertions(+), 17 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/powernv.h b/arch/powerpc/platforms/powernv/powernv.h
index e297bf4abfcb..fd3f5e1eb10b 100644
--- a/arch/powerpc/platforms/powernv/powernv.h
+++ b/arch/powerpc/platforms/powernv/powernv.h
@@ -42,4 +42,6 @@ ssize_t memcons_copy(struct memcons *mc, char *to, loff_t pos, size_t count);
u32 __init memcons_get_size(struct memcons *mc);
struct memcons *__init memcons_init(struct device_node *node, const char *mc_prop_name);

+void powernv_rng_init(void);
+
#endif /* _POWERNV_H */
diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c
index e3d44b36ae98..c1beced9c32c 100644
--- a/arch/powerpc/platforms/powernv/rng.c
+++ b/arch/powerpc/platforms/powernv/rng.c
@@ -17,6 +17,7 @@
#include <asm/prom.h>
#include <asm/machdep.h>
#include <asm/smp.h>
+#include "powernv.h"

#define DARN_ERR 0xFFFFFFFFFFFFFFFFul

@@ -28,6 +29,12 @@ struct powernv_rng {

static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);

+static struct {
+ struct powernv_rng rng;
+ spinlock_t lock;
+} early_state __initdata = {
+ .lock = __SPIN_LOCK_UNLOCKED(powernv_early_rng)
+};

int powernv_hwrng_present(void)
{
@@ -84,7 +91,7 @@ static int powernv_get_random_darn(unsigned long *v)
return 1;
}

-static int __init initialise_darn(void)
+static int __init initialize_darn(void)
{
unsigned long val;
int i;
@@ -98,10 +105,18 @@ static int __init initialise_darn(void)
return 0;
}
}
+ return -EIO;
+}

- pr_warn("Unable to use DARN for get_random_seed()\n");
+static int __init powernv_get_random_long_early(unsigned long *v)
+{
+ unsigned long flags;

- return -EIO;
+ spin_lock_irqsave(&early_state.lock, flags);
+ *v = rng_whiten(&early_state.rng, in_be64(early_state.rng.regs));
+ spin_unlock_irqrestore(&early_state.lock, flags);
+
+ return 1;
}

int powernv_get_random_long(unsigned long *v)
@@ -163,32 +178,51 @@ static __init int rng_create(struct device_node *dn)

rng_init_per_cpu(rng, dn);

- pr_info_once("Registering arch random hook.\n");
-
ppc_md.get_random_seed = powernv_get_random_long;

return 0;
}

-static __init int rng_init(void)
+void __init powernv_rng_init(void)
+{
+ struct device_node *dn;
+ struct resource res;
+
+ /* Prefer darn over the rest. */
+ if (!initialize_darn())
+ return;
+
+ dn = of_find_compatible_node(NULL, NULL, "ibm,power-rng");
+ if (!dn)
+ return;
+ if (of_address_to_resource(dn, 0, &res))
+ return;
+ early_state.rng.regs_real = (void __iomem *)res.start;
+ early_state.rng.regs = of_iomap(dn, 0);
+ if (!early_state.rng.regs)
+ return;
+ early_state.rng.mask = in_be64(early_state.rng.regs);
+ ppc_md.get_random_seed = powernv_get_random_long_early;
+}
+
+static __init int powernv_rng_late_init(void)
{
struct device_node *dn;
- int rc;
+
+ /*
+ * If this didn't get initialized early on, then we're using darn,
+ * or this isn't available at all, so return early.
+ */
+ if (ppc_md.get_random_seed != powernv_get_random_long_early)
+ return 0;
+ ppc_md.get_random_seed = NULL;

for_each_compatible_node(dn, NULL, "ibm,power-rng") {
- rc = rng_create(dn);
- if (rc) {
- pr_err("Failed creating rng for %pOF (%d).\n",
- dn, rc);
+ if (rng_create(dn))
continue;
- }
-
/* Create devices for hwrng driver */
of_platform_device_create(dn, NULL, NULL);
}
-
- initialise_darn();
-
return 0;
}
-machine_subsys_initcall(powernv, rng_init);
+machine_subsys_initcall(powernv, powernv_rng_late_init);
diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index 824c3ad7a0fa..a5fcb6796b22 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -203,6 +203,8 @@ static void __init pnv_setup_arch(void)
pnv_check_guarded_cores();

/* XXX PMCS */
+
+ powernv_rng_init();
}

static void __init pnv_init(void)
--
2.35.1

2022-06-21 14:21:24

by Jason A. Donenfeld

[permalink] [raw]

Subject: [PATCH v5] powerpc/powernv: wire up rng during setup_arch

The platform's RNG must be available before random_init() in order to be
useful for initial seeding, which in turn means that it needs to be
called from setup_arch(), rather than from an init call. Fortunately,
each platform already has a setup_arch function pointer, which means we
can wire it up that way. Complicating things, however, is that POWER8
systems need some per-cpu state and kmalloc, which isn't available at
this stage. So we split things up into an early phase and a later
opportunistic phase. This commit also removes some noisy log messages
that don't add much.

Cc: [email protected]
Cc: Michael Ellerman <[email protected]>
Reviewed-by: Christophe Leroy <[email protected]>
Fixes: a4da0d50b2a0 ("powerpc: Implement arch_get_random_long/int() for powernv")
Signed-off-by: Jason A. Donenfeld <[email protected]>
---
arch/powerpc/platforms/powernv/powernv.h | 2 +
arch/powerpc/platforms/powernv/rng.c | 47 ++++++++++++++++--------
arch/powerpc/platforms/powernv/setup.c | 2 +
3 files changed, 35 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/powernv.h b/arch/powerpc/platforms/powernv/powernv.h
index e297bf4abfcb..fd3f5e1eb10b 100644
--- a/arch/powerpc/platforms/powernv/powernv.h
+++ b/arch/powerpc/platforms/powernv/powernv.h
@@ -42,4 +42,6 @@ ssize_t memcons_copy(struct memcons *mc, char *to, loff_t pos, size_t count);
u32 __init memcons_get_size(struct memcons *mc);
struct memcons *__init memcons_init(struct device_node *node, const char *mc_prop_name);

+void powernv_rng_init(void);
+
#endif /* _POWERNV_H */
diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c
index e3d44b36ae98..e332e72e1857 100644
--- a/arch/powerpc/platforms/powernv/rng.c
+++ b/arch/powerpc/platforms/powernv/rng.c
@@ -17,6 +17,7 @@
#include <asm/prom.h>
#include <asm/machdep.h>
#include <asm/smp.h>
+#include "powernv.h"

#define DARN_ERR 0xFFFFFFFFFFFFFFFFul

@@ -28,7 +29,6 @@ struct powernv_rng {

static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);

-
int powernv_hwrng_present(void)
{
struct powernv_rng *rng;
@@ -98,9 +98,6 @@ static int __init initialise_darn(void)
return 0;
}
}
-
- pr_warn("Unable to use DARN for get_random_seed()\n");
-
return -EIO;
}

@@ -163,32 +160,50 @@ static __init int rng_create(struct device_node *dn)

rng_init_per_cpu(rng, dn);

- pr_info_once("Registering arch random hook.\n");
-
ppc_md.get_random_seed = powernv_get_random_long;

return 0;
}

-static __init int rng_init(void)
+static int __init powernv_get_random_long_early(unsigned long *v)
{
struct device_node *dn;
- int rc;
+
+ if (!slab_is_available())
+ return 0;
+
+ if (cmpxchg(&ppc_md.get_random_seed, powernv_get_random_long_early,
+ NULL) != powernv_get_random_long_early)
+ return 0;

for_each_compatible_node(dn, NULL, "ibm,power-rng") {
- rc = rng_create(dn);
- if (rc) {
- pr_err("Failed creating rng for %pOF (%d).\n",
- dn, rc);
+ if (rng_create(dn))
continue;
- }
-
/* Create devices for hwrng driver */
of_platform_device_create(dn, NULL, NULL);
}

- initialise_darn();
+ if (!ppc_md.get_random_seed)
+ return 0;
+ return ppc_md.get_random_seed(v);
+}
+
+void __init powernv_rng_init(void)
+{
+ /* Prefer darn over the rest. */
+ if (!initialise_darn())
+ return;
+
+ if (of_find_compatible_node(NULL, NULL, "ibm,power-rng"))
+ ppc_md.get_random_seed = powernv_get_random_long_early;
+}

+static int __init powernv_rng_late_init(void)
+{
+ unsigned long v;
+ /* In case it wasn't called during init for some other reason. */
+ if (ppc_md.get_random_seed == powernv_get_random_long_early)
+ powernv_get_random_long_early(&v);
return 0;
}
-machine_subsys_initcall(powernv, rng_init);
+machine_subsys_initcall(powernv, powernv_rng_late_init);
diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index 824c3ad7a0fa..a5fcb6796b22 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -203,6 +203,8 @@ static void __init pnv_setup_arch(void)
pnv_check_guarded_cores();

/* XXX PMCS */
+
+ powernv_rng_init();
}

static void __init pnv_init(void)
--
2.35.1

2022-06-21 18:52:44

by Jason A. Donenfeld

[permalink] [raw]

Subject: Re: [PATCH v5] powerpc/powernv: wire up rng during setup_arch

Hi Christophe,

On Tue, Jun 21, 2022 at 06:33:11PM +0000, Christophe Leroy wrote:
> Le 21/06/2022 à 16:08, Jason A. Donenfeld a écrit :
> > The platform's RNG must be available before random_init() in order to be
> > useful for initial seeding, which in turn means that it needs to be
> > called from setup_arch(), rather than from an init call. Fortunately,
> > each platform already has a setup_arch function pointer, which means we
> > can wire it up that way. Complicating things, however, is that POWER8
> > systems need some per-cpu state and kmalloc, which isn't available at
> > this stage. So we split things up into an early phase and a later
> > opportunistic phase. This commit also removes some noisy log messages
> > that don't add much.
>
> Regarding the kmalloc(), I have not looked at it in details, but usually
> you can use memblock_alloc() when kmalloc is not available yet.

That seems a bit excessive, especially as those allocations are long
lived. And we don't even *need* it that early, but just before
random_init(). Michael is running this v5 on the test rig overnight, so
we'll learn in the Australian morning whether this finally did the trick
(I hope).

Jason

2022-06-21 18:57:28

by Christophe Leroy

[permalink] [raw]

Subject: Re: [PATCH v5] powerpc/powernv: wire up rng during setup_arch

Le 21/06/2022 à 16:08, Jason A. Donenfeld a écrit :
> The platform's RNG must be available before random_init() in order to be
> useful for initial seeding, which in turn means that it needs to be
> called from setup_arch(), rather than from an init call. Fortunately,
> each platform already has a setup_arch function pointer, which means we
> can wire it up that way. Complicating things, however, is that POWER8
> systems need some per-cpu state and kmalloc, which isn't available at
> this stage. So we split things up into an early phase and a later
> opportunistic phase. This commit also removes some noisy log messages
> that don't add much.

Regarding the kmalloc(), I have not looked at it in details, but usually
you can use memblock_alloc() when kmalloc is not available yet.

Christophe

2022-06-21 19:43:32

by Christophe Leroy

[permalink] [raw]

Subject: Re: [PATCH v5] powerpc/powernv: wire up rng during setup_arch

Le 21/06/2022 à 20:47, Jason A. Donenfeld a écrit :
> Hi Christophe,
>
> On Tue, Jun 21, 2022 at 06:33:11PM +0000, Christophe Leroy wrote:
>> Le 21/06/2022 à 16:08, Jason A. Donenfeld a écrit :
>>> The platform's RNG must be available before random_init() in order to be
>>> useful for initial seeding, which in turn means that it needs to be
>>> called from setup_arch(), rather than from an init call. Fortunately,
>>> each platform already has a setup_arch function pointer, which means we
>>> can wire it up that way. Complicating things, however, is that POWER8
>>> systems need some per-cpu state and kmalloc, which isn't available at
>>> this stage. So we split things up into an early phase and a later
>>> opportunistic phase. This commit also removes some noisy log messages
>>> that don't add much.
>>
>> Regarding the kmalloc(), I have not looked at it in details, but usually
>> you can use memblock_alloc() when kmalloc is not available yet.
>
> That seems a bit excessive, especially as those allocations are long
> lived. And we don't even *need* it that early, but just before
> random_init(). Michael is running this v5 on the test rig overnight, so
> we'll learn in the Australian morning whether this finally did the trick
> (I hope).
>

The fact that they are long lived make them a good candidate for
memblock_alloc().

But fair enough, if they are not required that early then just do it later.

Christophe

2022-06-22 02:58:41

by Michael Ellerman

[permalink] [raw]

Subject: Re: [PATCH v5] powerpc/powernv: wire up rng during setup_arch

Christophe Leroy <[email protected]> writes:
> Le 21/06/2022 à 20:47, Jason A. Donenfeld a écrit :
>> On Tue, Jun 21, 2022 at 06:33:11PM +0000, Christophe Leroy wrote:
>>> Le 21/06/2022 à 16:08, Jason A. Donenfeld a écrit :
>>>> The platform's RNG must be available before random_init() in order to be
>>>> useful for initial seeding, which in turn means that it needs to be
>>>> called from setup_arch(), rather than from an init call. Fortunately,
>>>> each platform already has a setup_arch function pointer, which means we
>>>> can wire it up that way. Complicating things, however, is that POWER8
>>>> systems need some per-cpu state and kmalloc, which isn't available at
>>>> this stage. So we split things up into an early phase and a later
>>>> opportunistic phase. This commit also removes some noisy log messages
>>>> that don't add much.
>>>
>>> Regarding the kmalloc(), I have not looked at it in details, but usually
>>> you can use memblock_alloc() when kmalloc is not available yet.
>>
>> That seems a bit excessive, especially as those allocations are long
>> lived. And we don't even *need* it that early, but just before
>> random_init(). Michael is running this v5 on the test rig overnight, so
>> we'll learn in the Australian morning whether this finally did the trick
>> (I hope).
>
> The fact that they are long lived make them a good candidate for
> memblock_alloc().
>
> But fair enough, if they are not required that early then just do it later.

memblock works but then we trip on ioremap vs early_ioremap.

Fixing that is a bit of a pain as we'd have to stop using of_iomap() and
we'd also need to switch the mappings to ioremap() later in boot.

We'd also have to defer the percpu initialisation.

So it's all just a bit of a pain when we actually only need to get the
hook ready before random_init() which is called much later in boot when
slab/ioremap/percpu are all ready.

cheers

2022-06-26 00:45:57

by Michael Ellerman

[permalink] [raw]

Subject: Re: [PATCH v5] powerpc/powernv: wire up rng during setup_arch

On Tue, 21 Jun 2022 16:08:49 +0200, Jason A. Donenfeld wrote:
> The platform's RNG must be available before random_init() in order to be
> useful for initial seeding, which in turn means that it needs to be
> called from setup_arch(), rather than from an init call. Fortunately,
> each platform already has a setup_arch function pointer, which means we
> can wire it up that way. Complicating things, however, is that POWER8
> systems need some per-cpu state and kmalloc, which isn't available at
> this stage. So we split things up into an early phase and a later
> opportunistic phase. This commit also removes some noisy log messages
> that don't add much.
>
> [...]

Applied to powerpc/fixes.

[1/1] powerpc/powernv: wire up rng during setup_arch
https://git.kernel.org/powerpc/c/f3eac426657d985b97c92fa5f7ae1d43f04721f3

cheers